As modern technology advances, many electronic components and devices have been scaled down to the micro regime aiming for faster and more portable operation. This has given rise to the emergence of micro-electromechanical systems (MEMS) technology that made use of semiconductor manufacturing technology for the fabrication of micro- and nano-devices. In line with the trend of development, there is a need to develop cost-effective processes that can be integrated easily in batch processing. Many modern magnetic MEMS devices (such as including micro-actuators, sensors, and frictionless micro-gears) require a magnetic film which can produce a high vertical magnetic field.
It is known to use electroplating to deposit various thin magnetic films for magnetic recording purposes. In contrast to many other thin-film deposition methods such as sputtering and evaporation, electroplating offers a much faster and cost-effective method of depositing thick (˜100 um) films with easy control of process parameters for achieving specific film characteristics. In line with the rising demand for microdevices, electroplating has been actively explored in recent years as a favorable method for deposition of high aspect ratio microstructures in the fabrication of MEMS devices [1-3] since it is compatible with many other microfabrication processes.
Cobalt-based alloys with the addition of Ni, P, As, Sb, Bi, W, Cr, Mo, Pt or Cu have been electroplated as either binary or ternary material systems [4-8]. However, there are not many studies on the vertical anisotropy of material systems fabricated by electroplating. So far, material systems such as CoNiP [9], CoMnP [10], CoNiMnP [10], CoPtWP [11] and CoPt [12,13] has been an attractive candidate under development as a hard magnetic material with high vertical magnetic anisotropy. Nevertheless, these reports have been limited to magnetic film thickness of a few microns (<10 um) which might not meet the requirement of many magnetic MEMS devices. In order to generate sufficient forces for microactuation purposes, substantial material volume is necessary hence the requirement for thick films. Although electroplated CoNiMnP in the form of thick array (40 um height) [14] has been reported to exhibit high vertical anisotropy by virtue of their magnetic array geometry, material systems of much higher intrinsic properties should be utilized so as to maximize the performance of devices.
In view of the above considerations, there is a need to develop new material of sufficient vertical magnetic property by a suitable process that is capable of thick film deposition.